Within political institutions insulated from money in politics and domestic electoral considerations, to what extent are non-state actors able to influence regulations? Many international organizations (IOs) are composed only of state members, but their regulations have far-reaching consequences for non-state actors. This paper sheds new light on the influence of non-state actors, particularly firms, on regulations, with a focus on the case of OECD tax evasion regulations. I argue that firms and industry associations work to build positive reputations with bureaucrats through broad-based and high-quality written public comments to further their policy preferences. I present evidence that bureaucrats make decisions in line with these expectations through quantitative analysis of a new dataset of 3,349 OECD public comments, natural language processing methods, and thirty-three in-depth interviews. The results indicate that stakeholder engagement may be a double-edged sword: while intended to democratize access to the policy-making process, even these fora are susceptible to strategic firm behavior. However, while well-resourced firms and associations are at an advantage in having their voice heard in the creation of regulations, smaller firms that invest substantially in the process can have an outsized influence. International taxation also represents a substantively important case of non-state actor influence given the successful co-ordination of 147 countries on new tax regulations.